Method and apparatus for implementing persistent and reliable message delivery

ABSTRACT

A method and apparatus provide for persistent caching of methods delivered via a publish-subscribe network. At a first node, a message having data via the network is received. The data is time-marked. The data is cached in a cache memory at the first node. The message is routed to a second node using content-based routing. These steps are repeated at a second node. A router that includes modules for executing this method is provided. A publish-subscribe network that includes nodes that include modules for executing this method is provided. A computer-readable medium that includes instructions for executing this method is provided.

REFERENCE TO RELATED APPLICATIONS

[0001] The present application incorporates by reference and claims thepriority of U.S. Provisional Application No. 60/369,832, entitled“Method and Apparatus for Implementing Persistent and Reliable MessageDelivery,” filed Apr. 3, 2002, and U.S. Provisional Application No.60/447,782, entitled “Propagating Content Filters, Content-Based PacketRouting Using Compact Filter Storage and Off-Line Pre-computation,Reliable Publishing and Subscribing, Implementing Persistent andReliable Message Delivery, and Implementing Query-Response InteractionsBy Mapping Data Advertisements as Subscriptions and Queries asNotifications in a Publish-Subscribe Network,” filed Feb. 19, 2003. Thepresent application is also a Continuation-in-Part (CIP) of U.S. patentapplication Ser. No. 10/199,356, entitled “Packet Routing Via PayloadInspection,” U.S. patent application Ser. No. 10/199,368, entitled“Method And Apparatus For Content-Based Routing And Filtering At RoutersUsing Channels,” U.S. patent application Ser. No. 10/199,439, entitled“Method For Sending And Receiving A Boolean Function Over A Network”,U.S. patent application Ser. No. 10/199,369, entitled “Method ForStoring Boolean Functions To Enable Evaluation, Modification, Reuse, AndDelivery Over A Network,” and U.S. patent application Ser. No.10/199,388, entitled “Efficient Implementation of Wildcard Matching OnVariable-Sized Fields In Connect-Based Routing,” all filed Jul. 19, 2002and all hereby incorporated by reference.

[0002] The present application also incorporates by reference thefollowing U.S. patent applications, also CIPs of the above-referencedapplications, filed herewith: application Ser. No. ______, entitled“Method and Apparatus for Reliable Publishing and Subscribing in anUnreliable Network,” application Ser. No. ______, entitled “Method andApparatus for Propagating Content Filters For a Publish-SubscribeNetwork,” application Ser. No. ______, entitled “Method and Apparatusfor Content-Based Packet Routing Using Compact Filter Storage andOff-Line Pre-computation,” and, application Ser. No. ______, entitled“Method and Apparatus for Implementing Query-Response Interactions in aPublish-Subscribe Network.”

BACKGROUND OF THE INVENTION

[0003] Network bandwidth is increasing exponentially. However, thenetwork infrastructure (including routers, servers, daemons, protocols,etc.) is still using relatively old technologies. As a result, Internetapplications and network routers cannot keep up with the speed of thebandwidth increase. At the same time, more and more devices andapplications are becoming network enabled. The load that these devicesand applications put on the network nodes have increased tremendously.The increase of network load and number of applications also makes thecomplexity of implementing and maintaining network applications muchhigher. As a result, the increase of network bandwidth and theubiquitous use of network devices and applications can cause problemsfor routing and transmission of data in the old network infrastructure,particularly when publishing content to subscribers.

[0004] A model for having networks push information from servers toclients is the publish-subscribe style. In this model, the serverbecomes a simplified publisher of its information, without regard towhich clients may be interested in that information or where they arelocated in the network. The clients become subscribers for information,with information delivered as it becomes available, potentially withoutregard to details about where in the network it was published. Thenetwork is then responsible for efficiently routing publishedinformation to subscribers, for matching information to activesubscriptions, and for doing all of this in a way that is transparent tothe publishers and subscribers.

[0005] Because the complexity of the server is greatly reduced in thepublish-subscribe model, the distinction between a heavyweight serverand a lightweight client can begin to disappear, or rather to merge intothe notion of a peer that can be either publisher, or subscriber, orboth. Numerous kinds of applications have a natural affinity forpublish-subscribe-style interaction between peers. A common themeunderlying many of these applications is that the information beingpublished and subscribed for is in the form of events. For example, aninvestor buys or sells a stock, causing the price of the stock tochange. A traffic incident occurs on a freeway, causing traffic on thefreeway to back up. A security hole in a software system is discovered,causing a patch to be developed for the users of the software. A playerfires a weapon in an Internet game, causing another player's avatar todie. All of these exemplary phenomena are events that are potentially ofinterest to large numbers of subscribers and can be propagated over anetwork to notify those subscribers that the events happened. An eventis thus simply a self-contained, succinct piece of information aboutsomething potentially interesting that happened at some point in time atsome place on the network.

[0006] Another example involves a scheduled broadcast, which hasdiffering characteristics from applications involving only asynchronousevents where the time of events is unpredictable and random. First, theevent is scheduled to take place at a known time. Secondly, an eventdoes not need to be a succinct piece of information. Instead, it couldbe a massive amount of data. Directing this massive load of data to theparts of the network where interested subscribers are found requiressubstantial server processing.

[0007] Typically the server or publisher performs the routing decisionsfor the network in order to instruct the network on where to sendpublished content in the publish-subscribe model. The publisher storesthe subscriptions for content that it publishes. Upon receiving orgenerating new content, the publisher compares the content with each ofthe subscriptions to identify any matches. If the content (event)satisfies any subscriptions, the publisher pushes the content to thecorresponding subscriber via the network. This conventionalpublish-subscribe model places a tremendous burden on the publishers,particular as more devices become network-enabled and as the number ofsubscriptions increases. A complementary approach can be just asodious—a subscriber evaluates its own subscriptions on all publishedevents.

[0008] With greater convergence of untold numbers of applications acrossthe Internet, the possibilities for exploiting event notification becomeendless. However, those possibilities require a more efficient way tomake routing decisions and determine when events satisfy subscriptions,alleviating the burden on the publishers. Thus, a pervasive, persistentevent notification service could provide tremendous value-added benefitfor Internet applications, as well as other applications andimplementations.

SUMMARY OF THE INVENTION

[0009] A method and apparatus provide for providing persistence ofmessages transmitted via a network. Messages are received via thenetwork. The messages are stored for later retrieval. Persistent andreliable delivery of the messages is provided in response to failuresrelating to the network.

[0010] Another method and apparatus provide for persistent caching ofmethods delivered via a publish-subscribe network. At a first node, amessage having data via the network is received. The data istime-marked. The data is cached in a cache memory at the first node. Themessage is routed to a second node using content-based routing. Thesesteps are repeated at a second node. A router that includes modules forexecuting this method is provided. A publish-subscribe network thatincludes nodes that include modules for executing this method isprovided. A computer-readable medium that includes instructions forexecuting this method is provided.

[0011] Still another method provides for persistent caching of messagesdelivered via a publish-subscribe network. The method includes receivinga message having data via the publish-subscribe network, time-markingthe data, caching the data in a cache memory, determining if a timegranularity G has passed since the caching step, moving the cached datato a disk based on a determination that G has passed, determining if apersistent time-frame T has passed since the caching step for a lastblock of the cached data, and deleting the cached data from the diskbased on a determination that T has passed for the last block of thecached data. A router that includes modules for executing this method isprovided. A publish-subscribe network that includes nodes that includemodules for executing this method is provided. A computer-readablemedium that includes instructions for executing this method is provided.

[0012] Yet another method provides persistent caching of messagesdelivered via a publish-subscribe network. The method includes (a)receiving a plurality of messages having data via the network at aplurality of upstream nodes, (b) time-marking the data, (c) caching thedata in cache memories at the plurality of upstream nodes, (d) routingthe messages to an edge node using content-based routing and, (e)repeating steps (a) through (c) at the edge node, wherein the data iscached in a cache memory at the second node. A publish-subscribe networkthat includes a plurality of upstream nodes and an edge node, the nodesincluding modules for executing this method, is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are incorporated in and constitute apart of this specification and, together with the description, explainthe advantages and principles of the invention.

[0014]FIG. 1 is a diagram illustrating intelligent routing in a networkcore.

[0015]FIG. 2 is a network diagram illustrating intelligent routers forpublishers and subscribers.

[0016]FIG. 3 is a diagram illustrating a network infrastructure forintelligent routers and backbone routers.

[0017]FIG. 4 is a diagram of hardware components of an intelligentrouter.

[0018]FIG. 5 is a diagram of publisher and subscriber machines.

[0019]FIG. 6 is a diagram of channel managers for intelligent routers.

[0020]FIG. 7 is a diagram of software components in a user machine forinterfacing the machine with intelligent routers

[0021]FIG. 8 is a diagram of software components for an intelligentrouter.

[0022]FIG. 9 is a diagram of a packet structure for a message.

[0023]FIG. 10 is a flow chart of a publisher method.

[0024]FIG. 11 is a flow chart of a subscriber method.

[0025]FIG. 12 is a diagram of channel and subscriber screens.

[0026]FIG. 13 is a flow chart of a content-based routing method.

[0027]FIG. 14 is a flow chart of a caching method.

[0028]FIG. 15 is a diagram illustrating a cache index.

[0029]FIG. 16 is a flow chart of an agent method for an outgoingmessage.

[0030]FIG. 17 is a flow chart of an agent method for an incomingmessage.

[0031]FIG. 18 is a diagram illustrating an example of encoding of amessage.

[0032]FIG. 19 is a diagram of a database structure for storingsubscriptions.

[0033]FIG. 20 is a flow chart of a wildcard method.

[0034]FIG. 21A is a block diagram illustrating components of apersistent publish-subscribe network.

[0035]FIG. 21B is a diagram illustrating embodiments of cache managerroutines.

[0036]FIG. 21C is a flowchart of a persistent caching method.

[0037]FIG. 21D is a flowchart of a persistent message retrieval method.

DETAILED DESCRIPTION Overview

[0038] An Internet-scale, or other distributed network-scale, eventnotification system provides applications with a powerful and flexiblerealization of publish-subscribe networking. In this system, anapplication program uses event notification application programinterfaces (APIs) to publish notifications and/or to subscribe for andreceive notifications about events occurring inside the network.

[0039] A notification in the system is given a subject, which is astring or other structure that classifies the kind of information thenotification encapsulates. Also, a notification is completed with a setof attributes containing information specific to the notification. Forexample, an application might publish notifications about transactionson the New York Stock Exchange using the subject quotes.nyse andattributes symbol and price. The application might publish an individualnotification having specific attribute values, for example with symbolequal to SNE (the stock ticker symbol for Sony Corporation) and priceequal to 85.25. Most if not all of the attributes in a notification arepredefined, in the sense that they are found in all notifications forthe same family of subjects. However, publishers can add discretionaryattributes on a per-notification or other basis in order to provideadditional event-specific information. Therefore, not all or even anyattributes need be predefined.

[0040] In this system, subscribers are not restricted to subscribingonly for subjects or whole channels. Channels are further explained anddefined below. They can include an hierarchical structure specifying,for example, a subject field and one or more levels of relatedsub-fields (sub-subjects). Thus, subscribers can provide much morefinely-tuned expressions of interest by specifying content-based filtersover the attributes of notifications. For example, a subscriber mightsubscribe for all notifications for the subject quotes.nyse havingsymbol equal to SNE and price greater than 90.00 (indicating perhaps asell opportunity for a block of shares owned by the subscriber). Allnotifications matching the subscription can be delivered to thesubscriber via a callback or other type of function that the subscriberprovides at the time it registers its subscription or at other times.One subscription can be broken down into many filters.

[0041] The callback can perform many computations, including somethingas simple as writing a message to a terminal or sending an e-mail, tosomething more complex such as initiating the sale of a block of shares,and to something even more complex that initiates new publish-subscribeactivity (for example, replacing the existing subscription with a newsubscription for a buy opportunity at a price of 75.00, or publishing anew notification that the subscriber's portfolio has been modified).

[0042] Applications are aided in their publishing and subscribingactivities by agents, for example. The agents can possibly make use ofor be implemented with proxies. The agents, when used, provide networkconnectivity for outgoing notifications and subscriptions and deliveryof incoming matching notifications to subscribers. Once a notificationenters the network, the system's network of routers propagate thenotifications to all subscribers whose subscriptions match thenotification. One way of accomplishing this would be to broadcast thenotification to all points of the network and then let the applicationagents decide whether the notification is relevant to their subscribers.However, this is not necessarily a scalable approach—the network wouldusually be quickly overwhelmed by the load of message traffic,especially in the presence of large numbers of active and verbosepublishers. And even if sufficient bandwidth were not a problem, thesubscribers would be overwhelmed by having to process so manynotifications.

[0043] The system's exemplary network is much more efficient in the wayit routes notifications. First, it can use multicast routing to ensurethat a notification is propagated, for example, at most once over anylink in the network. Second, it can employ a large number ofsophisticated optimizations on filters to reduce as much as possible thepropagation of notifications.

[0044]FIG. 1 is a diagram conceptually illustrating this intelligentrouting in a network core. A publisher 14 transmits content in messagesvia an edge router 16 to a network core 10, used in a publish-subscribenetwork. A publish-subscribe network includes any type of network forrouting data or content from publishers to subscribers. The content istransmitted via one or more channels 18 representing logical connectionsbetween routers or other devices. An intelligent router 12 in networkcore 10 determines whether to route or forward the message. Inparticular, intelligent router 12 can determine if the message includescontent as subscribed to by a subscriber 24.

[0045] Each subscription encapsulates a subject filter and an attributefilter. Routers can possibly expand a subject filter to the set ofmatching subjects and merge attribute filters on a per-subject basis. Anintelligent router evaluates the subject filter against the subject ofnotifications, and evaluates the attribute filter against the attributevalues in notifications. The syntax for subject filters can possibly usewildcards, and the syntax for attribute filters can use Booleanexpressions, both of which are further explained below. The term“filter” is used to describe a set of events that a subscriber isinterested in receiving from publishers. Routing rules are generatedfrom the filters and are used by intelligent routers to make routingdecisions.

[0046] Therefore, if the entire filter set is not satisfied by a message26, for example, intelligent router 12 drops (discards) message 26,meaning that the message is not forwarded. If any filter of the entireset is satisfied by a message 20 according to the evaluations of subjectand attribute filters, for example, intelligent router 12 routes(forwards) message 20 via edge router 22 and possibly other devices to asubscriber 24, or performs other functions internal to router 12 withmessage 20, according to all the routing and/or action rules prescribedfor the matching filter. The search will continue until either theentire set of filters has been exhausted, or decisions about all therules have been obtained, whichever comes first.

[0047] This type of intelligent content-based routing in a network coreprovides for real-time data delivery of, for example, alerts andupdates. Examples of real-time data delivery for alerts include, but arenot limited to, the following: stock quotes, traffic, news, travel,weather, fraud detection, security, telematics, factory automation,supply chain management, and network management. Examples of real-timedata delivery for updates include, but are not limited to, thefollowing: software updates, anti-virus updates, movie and musicdelivery, workflow, storage management, and cache consistency. Manyother applications are possible for delivery of information forsubscriptions.

[0048] Table 1 illustrates storing of subscriptions with subjects andpredicates for the filtering. They can be stored in any type of datastructure, as desired or necessary, anywhere in the network. Asexplained below, the predicates are components of subscriptions. Thesubscriptions can be expressed in any way, examples of which areprovided below. TABLE 1 subscription 1 subject 1 predicate 1 . . .subscription N subject N predicate N

[0049] Table 2 provides an example of a publication and subscription fora quote server. This example is provided for illustrative purposes only,and subscriptions can include any number and types of parameters for anytype of data or content. TABLE 2 Quote Server Example Subject TreePublication Quotes.NYSE subject = Quotes.NYSE Quotes.AMEX AttributesQuotes.NASDAQ Symbol = SNE Price = 51 Volume = 1000000 AttributesSubscription Symbol Subject == Quotes.NYSE Price Filter Volume (Symbol== SNE) & (Price > 55)

[0050] The predicates provide the Boolean expressions for thesubscription and the subjects provide an indication of a channel for thesubscription. Subscriptions can be expressed in many different ways. Useof Boolean expressions is one such example and provides an ability toeasily convert the subscription into a subject filter and an attributefilter for content-based routing. Subscriptions can alternatively beexpressed without reference to a subject; however, use of a subject orchannel (further explained below) provides a context for interpretingand applying filters to attributes.

[0051] The routing decisions can be accomplished in the network core anddistributed throughout the network, alleviating processing burdens onpublisher and subscriber machines, and significantly enhancing theefficiency of the network. FIG. 1 illustrates one publisher, onesubscriber, and one intelligent router for illustrative purposes only;implementations can include many publishers, subscribers, andintelligent routers. The term intelligent router refers to a router orother entity having the ability to make routing decisions by inspectingthe payload of a packet or message in a network core or other locations.

Network Infrastructure

[0052]FIG. 2 is a network diagram illustrating intelligent routers forpublishers and subscribers. A routing entity 30 providing channelservices is, for example, effectively layered on a networkinfrastructure, as explained below, for routing messages amongintelligent routers. A publisher 32 conceptually includes, for example,an application 34 to receive an indication of published content, such asa pointer for retrieving the content, and an agent 36 to encode thecontent for network transmission via channel services 30. A collectionof logically interconnected intelligent routers 38, 40, 42, 44, 46, and48 route the content from the publisher using routing rules generatedfrom subject filters and attribute filters for subscriptions. Aplurality of links 39, 41, 43, and 45 provide the logical connectionsbetween intelligent routers 38, 40, 42, 44, 46, and 48. Other links 37and 47 provide, respectively, logical connections between publisher 32and intelligent router 38, and between a subscriber 54 and intelligentrouter 46. Subscriber 54 includes an agent 50 to detect and receive thesubscribed content, and an application 52 to present the content.

[0053] A channel can include, for example, a related set of logicalmulticast connections implemented in a distributed manner. A channel inthis exemplary embodiment is a logically related collection of networkresources used to serve a community of publishers and subscribersexchanging content. The content is classified according to the channelsubject namespace, and the resources are managed, controlled, andprovisioned via channel services provided by channel managers. Multiplechannels may share the same resources. Channels can provide a highlyscalable directory service such as, but not limited to, the followingexamples: publisher and subscriber information, authentication andauthorization information, message types, management information, andaccounting and billing information. Channels can also provide, forexample, persistence through caching, a fast data delivery mechanism,security, and user and network management. Channels can be used for anyother purpose as well.

[0054] The filtering by the intelligent routers can occur in a networkcore to distribute routing decisions. In addition, intelligent routerscan also function as edge routers connecting a user device, such as apublisher or subscriber, with the network core. Also, the same deviceconnected to the network can function as both a publisher to pushcontent to subscribers via routing decisions in the network and as asubscriber to received pushed content. The intelligent routers andchannels can be connected in any configuration, as necessary or desiredfor particular implementations, and the configuration shown in FIG. 2 isprovided for illustrative purposes only.

[0055]FIG. 3 is a diagram of an exemplary network infrastructure forintelligent routers and conventional backbone routers, also illustratinglogical connections for channels. The intelligent routers in thisexample use existing backbone routers in the network, such as theInternet or other distributed network, and the intelligent routers arethus effectively layered on the backbone routers. In this example,Internet Service Provider (ISP) networks 58, 59, and 60 each includeseveral backbone routers for conventional routing of messages orpackets. A plurality of intelligent routers 61-70 are connected with oneor more backbone routers in ISP networks 58, 59, and 60. Intelligentrouters 61-70 are also interconnected by a plurality of links 73-85,representing examples of links, and can be connected to end user devicesby the links as well. Intelligent routers 61-70 can be controlled by oneor more administrator machines such as an entity 71, and one or morevirtual private network (VPN) controllers such as an entity 72. The ISPnetworks 58, 59, and 60 would also be connected to publisher andsubscriber machines (not shown in FIG. 3). The backbone routers in andamong ISPs 58, 59, and 60 are interconnected in any conventional waywithin the existing network infrastructure.

[0056] The intelligent routers 61-70 and links 73-85, as illustrated,can be implemented using existing network infrastructure, and theyprovide for content-based routing in the network core. The links 73-85represent logical connections between intelligent routers 61-70 and canbe implemented using, for example, existing network infrastructure orother devices. A link, for example, can be implemented using a logicalconnection called the tunnel. A tunnel includes the hardware, andpossibly software, network infrastructure for implementing a link, andone tunnel can be a component of multiple channels. The channelsfacilitate content-based routing in the intelligent routers by providinglogical configurations for particular types of content and thusproviding a context for attributes transmitted over the channels.Although intelligent routers can perform routing decisions withoutchannels, the channels enhance the efficiency of content-based routingby the intelligent routers in the network core.

[0057] This exemplary embodiment includes use of channels and links. Alink is a connection between two routers—albeit intelligent routers. Achannel is a network entity encompassing a (typically large) collectionof routers, configured statically or dynamically by the interconnectinglinks to achieve one-to-many or many-to-many logical connections. Inparticular, a channel is a top-level logical entity describing theessential characteristics of the channel. Under one channel, there couldbe many subjects. Each subject will form a sub-network (such as amulticast tree) involving a collection of interconnected routers. Thesesubject-based sub-networks can be allocated, oriented, and configured indifferent manners. The channel, being a collection of all thesub-networks formed for the subjects under it, may resemble a mesh ofnetworks, for example.

[0058]FIG. 4 is a diagram of exemplary hardware components of anintelligent router 92, which can correspond with any of the otherreferenced intelligent routers. A network node 90 can includeintelligent router 92 connected with a conventional backbone router 95.Intelligent router 92 includes a processor 93 connected to a memory 94and a secondary storage 97 (possibly implemented with a detachedmachine, for example), either of which can store data, as well as cachedata, and store applications for execution by processor 93. Secondarystorage 97 provides non-volatile storage of data. Under software controlas explained below, processor 93 provides instructions to backbonerouter 95 for it to route (forward) or not route (discard) messages orpackets based upon routing rules generated from subject filters andattribute filters for subscriptions. Although shown as implemented in aseparate processor-controlled device, intelligent router 92 canalternatively be implemented in an application specific integratedcircuit (ASIC) within backbone router 95 to provide the intelligentrouting functions in hardware possibly with embedded software. Theintelligent routing functions can also be alternatively implemented in acombination of software and hardware in one or multiple routing devices.

[0059]FIG. 5 is a diagram of exemplary publisher and subscribermachines. A publisher machine 100 or 118 can include the followingcomponents: a memory 102 storing one or more publisher applications 104and an agent application 105; a secondary storage device 112 providingnon-volatile storage of data; an input device 108 for enteringinformation or commands; a processor 114 for executing applicationsstored in memory 102 or received from other storage devices; an outputdevice 110 for outputting information; and a display device 116 forproviding a visual display of information.

[0060] A subscriber machine 122 or 140 can include the followingcomponents: a memory 124 storing one or more applications 126 and anagent application 128; a secondary storage device 130 providingnon-volatile storage of data; an input device 132 for enteringinformation or commands; a processor 134 for executing applicationsstored in memory 124 or received from other storage devices; an outputdevice 136 for outputting information; and a display device 138 forproviding a visual display of information. Publisher and subscribermachines can alternatively include more or fewer components, ordifferent components, in any configuration.

[0061] Publisher machines 100 and 118 are connected with subscribermachines 122 and 140 via a network 120 such as the network describedabove. Network 120 includes intelligent routers for providingdistributed routing of data or content in the network core via packetsor messages. Although only two publisher and subscriber machines areshown, network 120 can be scaled to include more publisher andsubscriber machines. The publisher and subscriber machines can beimplemented with any processor-controlled device such as, but notlimited to, the following examples: a server; a personal computer; anotebook computer; a personal digital assistant; a telephone; a cellulartelephone; a pager; or other devices. Network 120 with intelligentrouters can include any wireline or wireless distributed network,connecting wired devices, wireless devices, or both. Network 120 canalso potentially use existing or conventional network infrastructure.

[0062]FIG. 6 is a diagram illustrating channel managers 150 forintelligent routers. In this example, channel managers 150 areimplemented with multiple servers 152, 154, and 156. Each serverincludes its own local storage 158, 160, and 162. Intelligent routers164, 166, and 168 contact channel managers for information aboutparticular channels. The channel managers can also provide for datapersistence, fail over functions, or other functions. The channelmanagers thus provide the channel services, which include a database orset of databases anywhere in the network specifying, for example,channel-related information, properties for data persistence, userinformation for publishers and subscribers, and infrastructureinformation. The infrastructure information can include, for example, anidentification of intelligent routers and corresponding tunnelsconnecting them, subjects for the channels, and attributes for thechannels (a name and type for each attribute). Packets or messages canalso carry channel-related information including identification of fixedattributes and variable attributes.

[0063] A user when on-line can download channel information. Forexample, a user can register by using a user name and password. Uponauthenticating the user's log-on, the user can open (invoke) a channeland retrieve information about the channel from the channel managers.Publishers can use that information in publishing content, andsubscribers can use that information for entering and registeringsubscriptions.

[0064] Each channel manager 152, 154, and 156, in this example, acts asa primary for each intelligent router. In particular, each intelligentrouter is provided two Internet Protocol (IP) addresses in this example,one for a primary channel manager and another for a back-up channelmanager. The intelligent routers use those IP addresses to contact achannel manager and retrieve channel information. If the primary fails,an intelligent router can contact a back-up channel manager. The channelmanagers 152, 154, and 156 thus share data, as indicated by the linesconnecting them, concerning channel properties and other information.Each channel manager also has a designated back-up so that if thechannel manager fails, another one can take over processing for it.Devices in the network can use commands, for example, to retrievechannel information, examples of which are provided in Table 3.Intelligent routers can alternatively only have a primary channelmanager or more than two channel managers.

[0065]FIG. 7 is a diagram of exemplary software components in a stack180 in a user machine or device for connecting it with a network havingintelligent routers. The user machine can be used as a publisher,subscriber, or both, and it can include the exemplary devices identifiedabove. Stack 180 can include one or more user applications 182, whichcan provide for receiving subscriptions from a user, receiving channelinformation from a publisher, or receiving content or data to bepublished. User application 182 can also include any other type ofapplication for execution by a user machine or device.

[0066] The stack 180 can also include, for example, an agent 184, anevent library 186, a cache library 188, a channel library 190, amessaging library 192, and a dispatcher library 194. Agent 184 providesfor establishing network connections or other functions, and Table 3provides examples of commands implemented by agent 184, which can useproxy commands or other types of commands. Event library 186 logs eventsconcerning a user machine or other events or information. Cache library188 provides for local caching of data. Channel library 190 storesidentifications of channels and information for them. Dispatcher library194 provides connections with a control path 196, a channel manager 198,and one or more intelligent routers 200, and it can include theexemplary functions identified in Table 4. Messaging library 192provides a connection with a data path 204.

[0067] Tables 5-9 provide examples of messaging APIs in the Cprogramming language. Tables 5 and 6 provide examples of APIs to sendand retrieve messages. Tables 7 and 8 provide examples of APIs to sendand retrieve notifications. Table 9 provides examples of APIs to sendand retrieve control messages. These APIs and other APIs, programs, anddata structures in this description are provided only as examples forimplementing particular functions or features, and implementations caninclude any type of APIs or other software entities in any programminglanguage. TABLE 3 Examples of Agent Commands command functionpc.chn.open open channel, retrieve all information for channel, andlocally cache it pc.chn.close close channel pc.chn.getRouterInforetrieve information for routers on channel pc.chn.getAttributeInforetrieve information for attributes of channel pc.chn.getPropertiesretrieve properties for channel

[0068] TABLE 4 Dispatcher Functions Server-Side Listens for connections(sits on accept). Creates a thread to handle each connection. The threadis responsible for receiving and processing all requests coming on thatconnection. Client-Side Creates a thread that initiates a connection andis responsible for receiving and processing all data coming into theconnection.

[0069] TABLE 5 Example of API to Send a Message PC_StatusPC_msg_init(ChannelHandle ch, PC_UINT chld, PC_UINT userid, PC_TypeInfo*MsgType, PC_UINT msgTypeSize, PC_msg_SessionHandle *sess); PC_StatusPC_msg_cleanup(PC_msg_SessionHandle sess); PC_StatusPC_msg_closeTransport(PC_msg_SessionHandle sess); PC_StatusPC_msg_create(PC_msg_SessionHandle s, PC_msg_DataType dType,PC_msg_MsgHandle *msg); PC_Status PC_msg_delete(PC_msg_MsgHandle msg);PC_Status PC_msg_clone(PC_msg_MsgHandle org, PC_msg_MsgHandle *new);PC_Status PC_msg_setSubject(PC_msg_MsgHandle msg, PC_CHAR *subject);PC_Status PC_msg_setSubjectint(PC_msg_MsgHandle msg, PC_USHORT*subjectArray, PC_UINT arraySize); PC_StatusPC_msg_setAttrByNameInt(PC_msg_MSGHandle msg, const PC_CHAR *name,PC_INT value); // for each type PC_StatusPC_msg_setAttrByPosInt(PC_msg_MsgHandle msg, PC_UINT attributePos,PC_INT Value); // for each type PC_StatusPC_msg_addAttrInt(PC_msg_MsgHandle msg, const PC_CHAR *name, PC_INTvalue); // for each type PC_Status PC_msg_send(PC_msg_MsgHandle msg);

[0070] TABLE 6 Example of API to Retrieve a Message typedefstruct_attribute { PC_CHAR *name; PC_TypeCode type; void *value; PC_UINTarraySize; } PC_msg_Attribute; typedef struct_attributeArray { PC_UINTsize; PC_msg_Attribute **attrs; } PC_msg_AttributeArray; PC_StatusPC_msg_init(ChannelHandle ch, PC_UINT chld, PC_UINT userid, PC_TypeInfo*MsgType, PC_INT msgTypeSize, PC_msg_SessionHandle *sess); PC_StatusPC_msg_cleanup(PC_msg_SessionHandle sess); PC_StatusPC_msg_recv(PC_msg_SessionHandle sh, PC_msg_MsgHandle *msg); PC_StatusPC_msg_ctrlRecv(PC_msg_SessionHandle sh, PC_msg_MsgHandle *msg);PC_Status PC_msg_getSequenceNum(PC_msg_MsgHandle msg, PC_UINT *seqNo);PC_Status PC_msg_getPublisherInfo(PC_msg_MsgHandle msg,PC_msg_PublicInfo *pub); PC_Status PC_msg_getSubject(PC_msg_MsgHandlemsg, PC_CHAR **subject); PC_Status PC_msg_getSubjectInt(PC_msg_MsgHandlemsg, PC_USHORT **subjectArray, PC_INT *size); PC_StatusPC_msg_getDataType(PC_msg_MsgHandle hMsg, PC_msg_DataType *dataType);PC_Status PC_msg_getAttrByPosInt(PC_msg_MsgHandle msg, PC_UINT pos,PC_INT *val); // for each type PC_StatusPC_msg_getAttrValueByNameInt(PC_msg_MsgHandle msg, const PC_CHAR *namePC_INT *val); PC_Status PC_msg_getAttrTypes(PC_msg_MsgHandle msg,PC_TypeCode* Types, PC_INT *arraySize); PC_StatusPC_msg_getAttributeByPos(PC_msg_MsgHandle msg, PC_UINT attributePos,PC_msg_Attribute **attr); PC_StatusPC_msg_getAttributeByName(PC_msg_MsgHandle msg, const PC_CHAR *namePC_msg_Attribute **attr); PC_StatusPC_msg_getPredefinedAttributes(PC_msg_MsgHandle msg,PC_msg_AttributeArray **attrs); PC_StatusPC_msg_getDiscretionaryAttributes(PC_msg_MsgHandle msg,PC_msg_AttributeArray **attrs); Void PC_msg_freeAttribute(PC_msgAttribute *attr); VoidPC_msg_freeAttributeArray(PC_msg_AttributeArray*attrArray);

[0071] TABLE 7 Example of API to Send a Notification ChannelHandle ch;PC_msg_MsgHandle msg; PC_msg_SessionHandle sh; PC_msg_TypeInfo Types[2]; Types [0].type = PC_STRING_TYPE; Types [0].name = “company”Types [1].type = PC_INT_TYPE; Types [1].name = “stockvalue”PC_msg_init(ch, chld, userld, Types, 2, &sh) PC_msg_create(sh,PC_MSG_DATA, &msg); PC_msg_setAttrValueByNameInt(msg, “stockvalue”,100); PC_msg_setAttrValueByPosString(msg, 1, “PreCache”);PC_msg_addAttrString(msg, “comment”, “mycomments”); PC_msg_send(msg);PC_msg_delete(msg); PC_msg_closeTransport(sh); PC_msg_cleanup(sh);

[0072] TABLE 8 Example of API to Retrieve a Notification ChannelHandlech; PC_msg_MsgHandle msg: PC_msg_SessionHandle sh; PC_msg_TypeInfo Types[2]; PC_msg_AttributeArray *attrArray; PC_CHAR *company; PC_INTvalue; Types [0].type = PC_STRING_TYPE; Types [0].name = “company” Types[1].type = PC_INT_TYPE; Types [1].name = “stockvalue” PC_msg_init(ch,chld, userld, Types, 2, &sh); While (1) { PC_msg_recv(sh, &msg);PC_msg_getAttrValueByPosString(msg, 0, &company);PC_msg_getAttrValueByNameInt(msg, “stockvalue”, &value);PC_msg_getDynamicAttributes(msg, &attrArray);PC_msg_freeAttributeArray(attrArray); PC_msg_delete(msg); }PC_msg_closeTransport(sh); PC_msg_cleanup(sh);

[0073] TABLE 9 Example of APIs to Send and Retrieve Control MessagesSender Side Code Receiver Side Code ChannelHandle ch; ChannelHandle ch;PC_msg_MsgHandle mh; PC_msg_MsgHandle msg; Int chld = 10;PC_msg_init(ch, chld, subld, NULL, 0, &sh); // Get a Channel handle forchannel 10 PC_msg_init(ch, chld, publd, NULL, 0, for (;;) { &sh)PC_msg_recv(sh, &msg); PC_msg_create(th, PC_msg_getSubject(msg,&subject); PC_MSG_CONTROL, PC_msg_getAttrValueByNameInt( &mh); msg,“Channelld, &chld); PC_msg_setSubject(mh,PC_msg_getAttrValueByNameString( “#.ADD_SUBJECT”); msg, “Subject”,&subject); PC_msg_addAttrInt(mh,,“Channelld”, PC_msg_delete(msg); chld);} PC_msg_addAttrString(mh, PC_msg_closeTransport(sh); “Subject”,“Quote.cboe”); PC_msg_cleanup(sh); PC_msg_send(mh); PC_msg_delete(mh);

[0074]FIG. 8 is a diagram of exemplary software components 210 for anintelligent router such as those identified above and intelligent router92 shown in FIG. 4. Software components 210 can be stored in, forexample, memory 94 for execution by processor 93 in intelligent router92. Components 210 include, for example, a filtering daemon 212, adispatcher 214, a routing daemon 216, and a cache manager 218. Filteringdaemon 212 provides filtering for content-based routing to processcontent for subscriptions according to routing rules, as explainedbelow. Dispatcher 214 provides for communication of control messagessuch as those required for propagating filters via path 220, and thedispatcher can also provide for a single point of entry for users andone secure socket with channel managers, enhancing security of thenetwork. In other words, users do not directly contact channel managersin this example, although they may in alternative implementations.Dispatcher 214 uses control messages to obtain attributes (name-valuepairs) from a channel manager.

[0075] Routing daemon 216 provides for communication with a data path222, which can occur via a conventional backbone router as illustratedin FIG. 4 or other routing device. Cache manager 218 provides for localcaching of data at the network node including the correspondingintelligent router. The operation of cache manager 218 is furtherexplained below, and it provides for distributed caching of datathroughout the network core.

[0076] Content-based routing can be implemented at the kernel level, asan alternative to the application level. Memory accessible by the kernelis separate from that in the application layer. To have content-basedrouting running in the application requires, for example, that messagedata be copied from the kernel memory area to the application area, andswitching the context of the application from that of the kernel to thatof the routing application. Both can induce substantial overhead. Ifinstead the kernel is modified to support content-based routing, therouting could take place much faster being rid of the overhead describedabove.

[0077] With this feature of content-based routing in the kernel, therouting daemon 216 may or may not directly send or receive data via thedata path 222, depending on the implementation. The daemon is a processrunning in the application layer, pre-computing the content-basedrouting table to be injected into the kernel. Once injected, however,the routing table can be used by the kernel to make routing decisions.Similarly, the filtering daemon pre-computes the filtering table andinjects it into the kernel. In this kernel implementation, neither therouting daemon nor the filtering daemon would directly interact with thedata path.

[0078]FIG. 9 is a diagram of an example of a packet structure 230 for amessage possibly including content for subscriptions. A packet ormessage for use in content-based routing includes, for example, a headersection and a payload section. The header section specifies routing orother information. The payload section specifies data or content, or anindication of the data or content. Packet structure 230 includes an IPheader 232, a User Datagram Protocol (UDP) Transmission Control Protocol(TCP) header 234, a length value 238, one or more subject fields 240,and one or more attributes 242. Packet structure 230 illustrates a basicstructure for a length value and the subjects and attributes. A packetused in content-based routing can also include other or differentelements, such as those illustrated in the example of FIG. 18 explainedbelow, and packets for content-based routing can be configured in anymanner. Also, the attributes can include discretionary attributesappended to the end of a message, for example. These discretionaryattributes are ad-hoc information, for example, added by the publisher(or even routers) that cannot necessarily be conveyed using the messageformat prescribed for the channel.

Publisher and Subscriber Methodologies

[0079]FIG. 10 is a flow chart of an exemplary publisher method 250 foruse by a publisher to set-up a channel and publish content. Method 250can be implemented, for example, in software modules including agent 106for execution by processor 114 in publisher machine 100. In method 150,agent 106 in the publisher machine receives a publisher creation of aproxy for a channel (step 252). The proxy provides for communicationwith the network. Agent 106 determines a message format for the channelthrough an interface (step 253), and the format information can beobtained from, for example, the channel managers or other entities inthe network. Agent 106 sets up the proxy for the channel using thereceived channel information (step 254), which includes receivingattributes for the channel (step 256) and creating a notification on thechannel (step 258). The notification provides content for devices“listening” for content on the channel. The attributes define parametersand characteristics for the notification.

[0080] Agent 106 transmits an identifier (ID) of the channel and contentinformation to intelligent routers in the network core or elsewhere foruse in processing subscriptions (step 260). The publisher populates thenotification attributes with appropriate values (step 261), and thepublisher can then publish content on notification in accordance withthe channel attributes (step 262). Steps 260-262 in this exampleaccomplish publishing the notification, which can alternatively involvedifferent or additional steps depending upon a particularimplementation. Therefore, the information associated with anotification in this example is partitioned into an ordered sequence ofattributes, each of which has a name, a position within the notification(starting at 1), a type, and a value. Alternatively, attributes can havedifferent characteristics depending upon a particular implementation.Attributes can include, for example, predefined attributes,discretionary attributes, or both.

[0081] The intelligent routers can use the channel ID in a packet toobtain the attributes for the corresponding channel, which determinesthe structure or format for packets transmitted via the channel. Inparticular, each packet can contain, for example, a tag associated witha channel ID and other header information such as a publisher ID andsubjects. The tags can be used to map subjects to numbers in the messageformat, an example of which is shown in FIG. 18. Small integer values,for example sixteen bit values, can be used for the numbers,Alternatively, any other type of numbers or information can be used tomap the subjects. Mapping subjects to numbers can provide particularadvantages; for example, it can save space in the message format andprovide a uniform or standard way to specify indications of the subjectsin the message so that they can be quickly located and identified.Intelligent routers can locally store the mapping or, alternatively, usethe numbers to remotely obtain the corresponding subject through acommand.

[0082] Table 10 illustrates a structure for mapping numbers to subjects,in this example using integer values. The subject tree parameter in thetable indicates that a subject can include one or more subject fields inan hierarchical relationship; for example, a subject tree can include astring of subject fields demarcated by particular symbols. Examples ofsubject trees are provided in Table 2. As an example, a subject treequotes.nyse includes a subject “quotes” and a sub-field “nyse” withthose two terms demarcates by a “.” as found in URLs or other networkaddresses. Aside from using periods and specifying URL-type strings,subject trees can be specified in any way using any characters andsymbols for demarcation. TABLE 10 Number Subject Tree integer value 1subject tree 1 integer value 2 subject tree 2 . . . integer value Nsubject tree N

[0083] Thus, knowing the packet format or structure for a particularchannel, the intelligent routers can quickly locate subjects andattributes, or other information, in the packet for content-basedrouting. For example, a channel can specify byte positions of subjectsand attributes transmitted over the channel, making them easy to locateby counting bytes in the packet. Alternatively, intelligent routers canparse packets to locate subjects and attributes, or other information.

[0084] Table 11 provides an example of a publisher program in the C++programming language. Table 12 provides an example of an API to create achannel. Table 13 provides an example of a channel configuration filemaintained by a channel manager (see FIG. 6) and providingchannel-related information, as illustrated. The system canalternatively have a global channel manager providing IP addresses ofgeographically dispersed servers functioning as local channel managersin order to distribute the processing load. TABLE 11 Example ofPublisher Program #include “PC_evn_Notification.h” #include“PC_evn_Proxy.h” using namespace precache::event; int main(int argc,char argv[]) { PC_UINT QuotesRUs = myChannelofInterest; // channel IDPC_UINT myID = myPublisherID; // publisher ID try { Proxy p(QuotesRUs,myID); Notification n1(p, “quotes.nyse”); n1.SetPredefinedAttr(“symbol”,“LUS”); n1.SetPredefinedAttr(price”, 95.73); p.Publish(n1); Notificationn2(p, “quotes.nyse”); n2.SetPredefinedAttr(1, “SNE”);  // attributesymbol is in position 1 n2.SetPredefinedAttr(2, 80.18);  // attributeprice is in position 2 p.Publish(n2); } catch (InvalidChannelExceptionicex) { cerr << “bad channel” << endl; } catch InvalidSubjectExceptionisex) { } catch (InvalidNotificationException inex) { cerr << “badnotification” << endl; } catch (Exception ex) { cerr << “unknown error”<< endl; } }

[0085] TABLE 12 Example of API to Create a Channel PC_Status rc; rc =PC_chn_create(Provider_info, authinfo, ConfigurationFile, &hChannel); /*the first one primary channel manager */ rc = PC_chn_addChannelManager(hChannel, “10.0.1.1”); /* secondary channel manager */ rc =PC_chn_addChannelManager (hChannel, “10.0.2.2”); */ rc =PC_chn_setProperties (hChannel, ConfigurationFile); /* Set the messagetype (only in fixed part of the message) by using rc =PC_chn_setAttributeType(hChannel, name, position, attributeType). Thetype information is propagated to all edge routers. */ rc =PC_chn_setAttributeType(hChannel,“Priority”,1,PC_UINT 16_TYPE); rc =PC_chn_setAttributeType(hChannel,“Alarm_Name”,2,PC_STRING_TYPE); rc =PC_chn_setAttributeType(hChannel,“Alarm_Time”,3,PC_INT32_TYPE); rc =PC_chn_updateAttribute(hChannel); rc = PC_chn_close(hChannel); /* finishchannel creation */

[0086] TABLE 13 Example of a Channel Configuration File # ChannelSetup - Read by Channel API, event and messaging # Each channel entryinformation is tagged with the # type of information e.g. # [ChannelComm5] for Channel 5 Communication related information # [ChannelSubjects 5]for subject related information in channel 5 # [ChannelAttributes 5] forattribute information in channel 5 # # The Channel id is appended to thetag to indicate # the channel that the information belongs to # e.g.[ChannelComm 5] indicates routing information # for channel 5. # # Allthe fields need not be set. For example if # running with the centralserver, the MulticastIP is # not needed. [ChannelComm 5]MulticastIP=225.0.0.1 RouterIP=test3 RouterPort=12345 ProxyPort=9015ProxyCtrlPort=9016 [ChannelSubjects 5] NumberOfSubjects=2subject1=#.SUBSCRIPTION mapping1=0.100 subject2=Quotes.Nysemapping2=102.101 [ChannelAttributes 5] NumberOfAttributes=4name1=StockId type1=PC_UINT_TYPE name2=Company type2=PC_CHARARRAY_TYPEname3=Price type3=PC_FLOAT_TYPE name4=Volume type4=PC_UINT_TYPE

[0087]FIG. 11 is a flow chart of a subscriber method 264 for use inreceiving and processing subscriptions. Method 266 can be implemented,for example, in software modules including agent 128 for execution byprocessor 134 in subscriber machine 122. In method 264, a graphical userinterface (GUI), for example, presents an indication of availablechannels to a user (step 266), which can be accomplished by application126. The information identifying the channels can be received from, forexample, the channel managers providing channel-related information. Anytype of application 126 can be used for presenting identifications ofchannels in any particular way or format. The application receives auser's selection of a channel (step 268) and calls an API or otherprogram for the selected channel (step 270). The API presentssubscription options to the user for the channel corresponding with theselected option (step 272). The API receives values for the subscriptionfrom the user (step 274) and sends the subscription to agent 128 forprocessing, as explained below (step 276).

[0088] The parameters for the subscription can include, for example, thepredicates as illustrated in Table 1. Each channel can use its own API,for example, in order to process subscriptions according to theparticular requirements or parameters for the corresponding channel.These APIs can include, for example, web-based or Java-based APIs forreceiving subscriptions and can use any type of user interface andprocessing to receive information for a subscription and pass it alongto the agent application.

[0089]FIG. 12 is a diagram conceptually illustrating channel andsubscriber screens or GUIs 278 and 284, which can be used in conjunctionwith method 264 for receiving a subscription. Screen 278 includes aplurality of sections 282 identifying available channels for selectionby a user. Upon selection of a particular channel, screen 284 can bedisplayed for receiving a user's values for the subscription in asection 286. A user can select a section 288 to submit the subscriptionor select a section 290 to cancel the subscription. Screens 278 and 284can be formatted as, for example, HyperText Markup Language (HTML) webpages or in any other format. Also, the screens can include anyconfiguration of sections and content, possibly including, for example,text, graphics, pictures, various colors, or multi-media information inorder to provide, as desired, a user-friendly and visually appealinginterface for subscribers. The screens can also include a toolbar 280providing, for example, conventional browser functions.

[0090] Table 14 provides an example of a subscriber program in the C++programming language. TABLE 14 Example of Subscriber Program #include<unistd.h> #include <iostream> #include “PC_evn_Filter.h” #include“PC_evn_Subscription.h” #include “PC_evn_Proxy.h” using namespaceprecache::event; class SubscriberApp : public Subscriber { private”:PC_UINT notificationCount = 0; public: SubscriberApp() {} // defaultconstructor void run() { PC_UINT QuotesRUs = myChannelofInterest; //channel ID PC_UINT myID = myPublisherID; // publisher ID try { Proxyp(QuotesRUs, myID); FilterFactory* factory =FilterFactory::GetFilterFactory(); Filter* f = factory->CreateFilter(p,“symbol == \“LU\””); PC_INT c1 = 0; SubscriptionHandle sh =p.Subscribe(“quotes.nyse”, f, this, (void*)&c1); while(notificationCount < 2) { //let notify() get some // notificationssleep(5); } p.Unsubscribe(sh); } catch (InvalidChannelException icex) {cerr << “bad channel” << endl; } catch (InvalidSubjectException isex) {cerr << “bad subject” << endl; } catch (InvalidChannelException ifex) {cerr << “bad filter” << endl; } catch(InvalidSubscriptionHandleException ishex) { cerr << “bas subscriptionhandle” << endl; } catch (Exception ex) { cerr << “unknown error” <<endl; } } void Notify(Notification* n, void* c) //this is the callbackmethod { if(*(PC_INT*)c == 0){//check the closure object PC_STRINGsymbol; PC_FLOAT price; n->GetPredefinedAttr(“symbol”, symbol);n->GetPredefinedAttr(“price”, price); cout << “The price of” << symbol<< “is” << price << endl; notificationCount++; } } }; int main(int argc,char argv[]) { SubscriberApp a; a.run(); }

Content-Based Routing Via Payload Inspection and Channels

[0091]FIG. 13 is a flow chart of a content-based routing via payloadinspection method 300. Method 300 can be implemented, for example, insoftware modules for execution by processor 93 in intelligent router 92,as represented by filtering daemon 212. Alternatively, it can beimplemented in an ASIC or a combination of hardware and software. Thecontent-based routing as illustrated in method 300 can be performed inintelligent routers anywhere in the network, such as in the network coreor in edge routers.

[0092] In a general sense, the content-based routing involves inspectinga payload section of a packet in order to determine how to process thepacket. This content-based routing methodology can include, for example,processing a list of subscriptions (using filters, for example) in anyorder, comparing a message subject-by-subject and attribute-by-attributewith routing rules to determine a routing for the message, andperforming the processing in a network core. The rules can include rulesgoverning in-router processing or any rules associated with a filter.These routing decisions can thus be distributed throughout a networkcore. The use of subjects as represented by channels determines amessage format, thus providing an intelligent router with a way ofquickly locating attributes within the message, for example by knowingtheir byte positions in the message or packet for a particular channel.

[0093] In method 300, intelligent router 92 receives a packet for amessage (step 302). It determines from the packet a channel ID for thecorresponding message (step 304) and retrieves attributes for thechannel using the channel ID (step 306). In this example, the type ofchannel (determined from the channel ID) determines locations and datatypes of attributes in the packet. The attributes for the channel can belocally stored or retrieved remotely such as via a channel manager.Intelligent router 92 retrieves a filter, which corresponds with asubscription (step 308). The filter includes one or more attributetests, usually a group of attribute tests for subscriptions. Intelligentrouter 92 applies attributes in the packet to the correspondingattribute test(s) in the filter description (step 310).

[0094] If all the attribute test(s) in the filter description produce apositive result (step 312), meaning the attributes satisfy all theattribute test(s), the intelligent router executes a set of functionsprescribed by the rules associated with the filter (step 314). Thesefunctions can include, for example, routing the packet to the next link,and/or performing some action or computation with the content of thepacket at the local router as prescribed by the rule(s). The action ornext link can be identified, for example, in a data structure specifyingthe corresponding subscription. When the rule is a link, it typicallyidentifies the next network node to receive the packet, which caninclude an intelligent router, backbone router, a network-connecteddevice, or other entity. Alternatively, the next links can be specifiedor associated with the subscriptions in other ways.

[0095] If all the attribute test(s) in the filter description did notproduce a positive result (step 312), meaning the attributes do notsatisfy all the attribute test(s), the filter is declared a mismatch(step 315). The intelligent router recursively follows the aboveprocedure until all the attribute tests in the filter description areexhausted or a first negative result is encountered, whichever comesfirst.

[0096] Once all the attribute tests have been processed for this filter,the intelligent router determines if more filters exist (step 316) and,if so, it returns to step 308 to retrieve the attribute test(s) for thenext filter to process the attributes for it. The matching procedure(steps 308, 310, 312, 314, 315, and 316) continues until either thecomplete set of filters is exhausted, or results for all the action orrouting rules can be determined, whichever comes first. If the packetdoes not satisfy any filter, it will be dropped (discarded) and notforwarded.

[0097] Intelligent router 92 can sequence through the filters in anyparticular order. For example, as illustrated in Table 15, intelligentrouter can store the filters for subscriptions in a file or routingtable and linearly sequence through them to apply the attributes tofilters (attribute tests). Alternatively, the routing table can includelinks or pointers to the filters.

[0098] The content-based routing can optionally use more than one methodat the same time, depending on the applications andperformance-enhancing heuristics such as the switching of algorithmsbased on traffic conditions, for example. The filters for the processingcan optionally be encrypted, decrypted, transformed, and merged at arouter in the network for use in performing inspecting of a payloadsection for the content-based routing. For example, a subscription suchas price>$3.54122 may be truncated to price>$3.54 because thepublications in the application are known not to contain currencyattributes beyond the second decimal points. Also, foreign currency maybe translated into U.S. currencies as well when a publication sent fromoverseas reaches the first router located in the U.S., for example.

[0099] As an alternative to a linear approach, intelligent router 92 canselect filters for processing in other orders or according to variousalgorithms that can possibly enhance the speed and efficiency ofprocessing. Table 16 provides examples of subscriptions andcorresponding links for them; in these examples, the subjects relate toa particular channel and the subscriptions for the subjects can berepresented by routing rules for the filters. The subjects can include,for example, network addresses such as Uniform Resource Locators (URLs)identifying a source of content. TABLE 15 Subscriptions Links Channel 1filter 1a links 1a filter 2a links 2a . . . . . . filter Na links na . .. Channel N filter 1N links 1a filter 2N links 1b . . . . . . filter NNlinks 1n

[0100] TABLE 16 Caching at Network Nodes Content Predicate Links sub =“quote.optimist” & x10, x11 ( ($1 > 5 & $2 = “LU”)  5 | ($1 > 30 & $2 =“T”) ) ( sub = “sony.music” | sub = “sony.movie” ) x11, x13 & $1 > 30 &$4 = “Beethoven” sub = “movie.ratings” & x11, s15 ($1 > 1999 | $2 =“Kurosawa”) & $3 = “**” 10

[0101]FIG. 14 is a flow chart of a caching method 320. Method 320 can beimplemented, for example, in software modules for execution by processor93 in intelligent router 92, as represented by cache manager 218.Alternatively, it can be implemented in an ASIC or a combination ofhardware and software, either in the same or different physical deviceas the corresponding intelligent router. In method 320, intelligentrouter 92 receives a message having data or content, a channel ID, andsubjects (step 322). Intelligent router 92 time marks the data (step324) and locally caches it such as in memory 94 or secondary storage 97(step 326). It indexes the cached data by, for example, channel ID,subjects, and time stamps (step 328).

[0102] If intelligent router 92 receives a request for data (step 330),it retrieves cached data, using the index, according to the request(step 332). Intelligent router 92 transfers the cached data to backbonerouter 95 or other routing entity for eventual transmission to therequestor or others. Method 320 can be repeatedly executed in order tocontinually cache data and retrieve cache data in response to requests.

[0103]FIG. 15 is a diagram illustrating a cache index (336) for use withmethod 320. Cache index (336) receives data (338) and stores it withtime stamps (340). As data is gathered, it is marked upon every durationof delta t, where delta t represents the time between marks, for examplet₂−t₁. Other types of indexes for time marking in any way canalternatively be used.

[0104] Table 17 conceptually illustrates indexing of cached data. Table18 conceptually illustrates a data structure for storing a connectionhistory for caching. Table 19 provides examples of data structures foruse in locally caching data in network nodes having intelligent routers.

[0105] The time marking can occur at any fixed or variable interval. Forexample, data can be cached and indexed every five minutes. Uponreceiving a command to retrieve cached data (such as #.getCache)specifying a time and subject, cache manager 218 uses the cache index todetermine if it can retrieve cached data corresponding with the requestfor step 332.

[0106] Each subject or channel can include, for example, its own IPaddress in a multicast tree and a set of intelligent routers. Therefore,Table 18 represents a connection history among such routers that can belocally stored a user machine; if an edge router fails, the machine canaccess the connection history to determine how to reconnect withupstream routers for the channel when the edge router comes backon-line. It can also execute a get cache command for the duration of thetime that it was disconnected in order to obtain any pending content forsubscriptions, for example. TABLE 17 t₁ channel ID 1 subjects 1-npointer 1 to cached data t₂ channel ID 2 subjects 1-n pointer 2 tocached data t_(n) channel ID N subjects 1-n pointer N to cached data

[0107] TABLE 18 Connection History time router network addresses t₁ R2UR2 UR3 t₂ R2 UR2 UR3 . . .

[0108] TABLE 19 Examples of Cache Data Structures for Intelligent RouterChannel Node Struct ChannelNode { PC_UINT unChanld; PC_AttributeInfo*pAttrinfo; PC_BOOL bPersistent; /* Persistent or RT*/ PC_UINTunTimeout; PC_UINT unTimeGranularity;/* in minutes */ PC_INT nDirFd;HashTable *pFirstLevelSubjs; } Subject Node Struct SubjectNode {PC_USHORT unSubjectld; PC_UINT unSubjLevel; Void pParent; /* Channel orSubject */ PC_INT nDirFd; HashTable *pNextLevelSubjs; DataNode *pData; }Data Node Struct DataNode { PC_INT nDirFd; SubjectNode *pParent;LastTimeGrainNode *pLastTGrainData; DLIST *pStoredData;/*listStoredTimeGrainNode */ PC_Mutex mStoredDataLock; } Stored Time GrainNode Struct StoredTimeGrainNode { PC_UINT unStartTime; /* in minutes*/Chanld; PC_UINT unEndTime; /* in minutes */ PC_INT nFd; } Last TimeGrain Node Struct LastTimeGrainNode { PC_CHAR pLastTGrainData; /* couldbe a list */ PC_UINT unLastTGrainStartTime; PC_BOOL bReadyToStore;PC_Mutex mCachedDataLock; }

[0109] These exemplary data structures include the followinginformation. A subject node contains a subject identifier, subjectlevel, pointer to parent channel or subject node, file descriptor forits own directory, pointer to hash table containing its next levelsubject nodes, and pointer to a data node. A data node contains apointer to its subject parent node, file descriptor for the datadirectory, circular buffer containing the data structures for the datastored on each storage device, head and tail of the buffer, and lock forlocking the data node during retrieval and storage. The stored timegrain node is the node representing the actual data file, and the lasttime grain node represents the last buffer that has not yet been storedto the storage device but is maintained in memory. The caching and datastorage threads in this example use the mutex of the last time grainnode for preventing concurrent access to the last time grain node.

Agent Processing

[0110]FIG. 16 is a flow chart of an agent method 350 for an outgoingsubscription message. Method 350 can be implemented, for example, insoftware modules as represented by agent 128 for execution by processor134 in user (subscriber) machine 122. In method 350, agent 128 receivesa subscription such as via the method described above in FIGS. 11 and 12(step 352). Agent 128 creates a string specifying a Boolean expressionfor the subscription (step 354) and parses the string to detect anyerrors in the subscription (step 356). If an error exists, agent 128 canpresent an error message to the user (step 360) in order for the user tocorrect the error and re-enter the subscription. If the subscriptioncontains no errors (step 358), agent 128 stores the expression in a datastructure, an example of which is provided below (step 362). Agent 128translates constituent not-equal expressions in the data structure topositive form (step 364) and translates the data structure to acorresponding disjunctive normal form (DNF) structure (step 366). Agent128 also simplifies AND expressions of the DNF structure to contain onlyrange filters and membership tests (step 368).

[0111] The DNF is a well-known canonical form in which a Booleanexpression is represented as an OR of one or more sub-expressions calleddisjuncts, each sub-expression being an AND of one or more attributetests. For example, the Boolean expression (price>=10 AND (symbol==“LU”OR symbol==“T”)) has an equivalent DNF representation of ((price>=10 ANDsymbol==“LU”) OR (price>=10 AND symbol==“T”)).

[0112] The transformation in step 364 involves translating expressionshaving the “not-equal” operator (represented in an exemplary syntax as!=) into an equivalent “positive” form that specifies all allowed valuesrather than the one disallowed value. This transformation is performedprior to creation of the DNF, and it is needed because the routers inthis example require formulae to be in positive form. For example, theexpression (price!=80) can be transformed to the equivalent positiveexpression (price<=79 OR price>=81).

[0113] The transformation in step 368 is performed after the DNF iscreated and involves an extra simplification of the resulting ANDexpressions, and it is also performed to simplify the work of therouters in this example. In particular, an AND of multiple attributetests for the same attribute can be simplified into a canonical “rangefilter” having either one lower bound, one upper bound, both a lower andupper bound, or a single value in the case of an equality test. Theparticular kind of range filter is then encoded according to Table 22.

[0114] For example, the expression (price>=10 AND price<=80 ANDprice>=20 AND price<=100) can be simplified to the expression (price>=20AND price<=80), which is an example of a range filter with both a lowerand an upper bound. Examples of the other kinds after simplification arethe following: (price>=20) (lower bound only); (price<=80) (upper boundonly); and (price==50) (single value). In creating these range filters,it is possible that some sub-expression will simplify to true or tofalse, in which case the sub-expression can be eliminated according tothe laws of Boolean algebra, thereby further optimizing the encoding ofthe expression in a message. For example, the expression (price>=50 ANDprice<=20) simplifies to false, since no value for “price” can satisfythe expression. In the special case in which a whole filter expressionsimplifies to false, the agent need not create a message at all, therebyrelieving the router of unnecessary work.

[0115] If the subject filter contains wildcards, agent 128 canoptionally convert them as explained below (step 370). Otherwise, anywildcards can be converted in the network, rather than on the usermachine or other device. In this exemplary embodiment, the syntax forsubject filters is the only syntax that uses wildcards, and the syntaxfor attribute filters is the only syntax that uses Boolean expressions.Alternatively, implementations can use different or varying types ofsyntax for subject filters and attribute filters.

[0116] Agent 128 encodes the resulting DNF expression into a message(step 372) and transfers the message to an intelligent router (step374). The encoding can involve converting the subscription to a flatmessage format, meaning that it constitutes a string of data. Thistransferring can involve propagating routing rules generated fromsubject filters and attribute filters for the subscription to one ormore intelligent routers or other routing entities in the network. Forthe propagation, the subscription expression can be mapped into aconventional packet structure, for example.

[0117] The encoding for step 372 involves marshalling subscriptions fora channel into a messaging format of the messaging API for propagationthroughout a channel. A subscription is internally messaged, forexample, as a notification with subject #.SUBSCRIPTION. Because thereare both a variable number of subject filter fields and a variablenumber of attribute tests, one pair of bytes is used to store the numberof subject filter fields, and another pair of bytes is used to store thenumber of attribute tests in this example. The individual fields of thesubject filter are marshaled sequentially, for example, in the order inwhich they were specified in the original subscription and are eachmarshaled into a two-byte portion of the message. Wildcard fields can bemarshaled as described below.

[0118] In marshaling the attribute tests, the operands of the tests aremarshaled at the end of the message in a manner similar to themarshaling of attribute values of notifications. Prior to marshaling theattribute tests and operands, they are sorted by attribute order withineach disjunct of the DNF with tests on predefined attributes in positionorder, followed by tests on discretionary attributes in name order.Furthermore, the set of relational tests on scalar valued attributeswithin each disjunct are simplified to a canonical form as range filtershaving either one limit (for left- or right-open ranges or equalitytests) or two limits (for closed ranges between distinct limits). Theremaining information about the tests is encoded into, for example,two-byte pairs in the same order as the operands; this sequence oftwo-byte pairs is placed in the message immediately following thesequence of two-byte encoding of subject filter fields. The two-bytepairs can constitute one form of a sequence of bit-string encodings ofattribute tests, which can also be used to represent other types ofencodings aside from two-byte pairs. Examples of attribute tests areprovided below.

[0119] The schema for the encoding of the attribute tests is depicted inTable 20. Table 21 illustrates encoding for the two-byte pairs, andTable 22 illustrates encoding of the Operator ID in the two-byte pairs.TABLE 20 Encoding Rules 1 A zero in the D bit indicates the beginning ofa new disjunct in the DNF, while a one in the D bit indicates anadditional conjunct within the current disjunct. 2 A value other thanall ones in the Notification Attribute Position indicates the positionof a predefined attribute (as defined by the channel's notificationtype) to which the test applies; the operand for the test is marshaledas depicted in the example shown in FIG. 18. 3 A value of all ones inthe Notification Attribute Position indicates that the test applies to adiscretionary attribute, in which case the name length and name of theattribute to which the test applies are marshaled with the operand. 4The bits for the Operand Type ID encode one of the predefined types forattributes. 5 The bits for the Operator ID encode the operator used inthe test, as defined in Table 22.

[0120] TABLE 21 First Byte 0 1 2 3 4 5 6 7 D Notification AttributePosition Second Byte 0 1 2 3 4 5 6 7 Operand Type ID Operator ID

[0121] TABLE 22 Operator Operator ID Left-open range 000 Right-openrange 001 Closed-range 010 Equality test 011 Positive membership test(in) 100 Negative membership test (not in) 101

[0122] Because the two-byte pair for a test already indicates both thetype of the operand of the test and whether or not the test applies to apredefined or discretionary attribute, there is no need to separatelymarshal the number of tests performed on discretionary attributes ortheir types. This scheme assumes there are no more than 127 predefinedattributes in a notification. Alternatively, this design may use morebits to encode attribute tests.

[0123] While this marshaling convention orders and groups attributetests according to the DNF of the attribute filter, an infrastructureelement (such as a router) may choose to evaluate the tests in someother order (perhaps according to dynamically derived local data aboutthe probability of success or failure of the different tests) in orderto make the overall evaluation of the attribute filter more efficient.The Subscription ID field of the message is a value generated by theagent for uniquely identifying the subscription to the agent's edgerouter in subsequent requests to modify or unsubscribe the subscription.In particular, a dynamic modification to the attribute filter of asubscription is propagated using the message format shown in the exampleof FIG. 18, except that the subject is #.RESUBSCRIPTION and theSubscription ID is that of the previously registered subscription beingmodified. And an unsubscription is propagated using, for example, themessage format of FIG. 18 up through the Subscription ID field, with thesubject being #.UNSUBSCRIPTION and the Subscription ID being that of thepreviously registered subscription being unsubscribed.

[0124] The following provides an example to illustrate the conversionand encoding by the agent as described above. Consider the followingexample attribute filter expression: price>=10 and (symbol==“LU” or(volume>=1000 and volume<=10000)). FIG. 19 presents a Unified ModelingLanguage (UML) diagram 390 depicting the objects used by the agent instep 362 to store the expression. This diagram illustrates anhierarchical relationship for specifying the subscription, which caninclude variables, constant values, or both. The objects in the diagramcan be instances of filter classes depending upon a particularimplementation. Each SimpleFilter object depicts the values ofattributes used to store information about a corresponding attributetest of the filter expression. In the expression of FIG. 19, an ORfilter 396 connects two AND filters 392 and 400. The AND filter 392contains a simple filter 394 with attributes for the subscription.Likewise, the OR filter 396 contains a simple filter 398, and the ANDfilter 400 contains simple filters 402 and 404.

[0125] For the purposes of this example, attributes price, symbol, andvolume are assumed to be predefined attributes of the associated channeland are assumed to be defined in positions 0, 1 and 2, respectively.Furthermore, the types of the attributes are assumed to be unsignedinteger (typecode 6), character array (typecode 12), and unsignedinteger (typecode 6), respectively.

[0126] Consider next a subscription containing the above exampleattribute filter expression as its attribute filter. FIG. 18 presentsthe marshaling of the subscription into a message. The schematic 386 onthe left side of FIG. 18 shows the actual message contents, while theschematic 388 on the right provides a legend for the different parts ofthe message. The width of each schematic in this example is four bytes.Prior to marshaling, the filter has been converted to its equivalentDNF: (price>=10 and symbol== “LU”) or (price>=10 and volume>=1000 andvolume<=10000).

[0127] The sixteen-bit attribute test encodings are shown as bitsequences, with gaps showing the separation into the different parts.Note that the two tests on price in this example cannot be combinedsince they are in separate disjuncts, and thus they are marshaledseparately as ranges that have no right bound (“right-open ranges”). Onthe other hand, the two tests on volume can be combined since they arein the same disjunct, and thus they are marshaled together as a single“closed-range” test.

[0128] Finally, note also that certain fields are characterized as being“assumed”; this means that values for these fields were chosenarbitrarily for this example and are in general independent of thesubscription that was marshaled. In addition, the subject filter for thesubscription was arbitrarily chosen to be “>,” which matches any subjectdefined by the associated channel. The example described above and shownin FIGS. 18 and 19 is provided for illustrative purposes only, and themarshalling can be used with any other type of subscription. Also,method 350 provides only one example of marshaling subscriptions, andthey can be marshaled in any other way.

[0129]FIG. 17 is a flow chart of an agent method 376 for an incomingmessage. Method 376 can be implemented, for example, by agent 128 andapplication 126 in user machine 122. In method 376, agent 128 receives amessage from an intelligent router corresponding with a subscription(step 378). Agent 128 determines a channel corresponding with thesubscription (step 380), for example by the channel ID in the message,and calls an API for the channel (step 382). The API present the datafor the subscription in a GUI or other format at the user machine (step384). The processing of incoming messages can use a process of decodingthe data in the reverse of the encoding process described above, andthis decoding (reverse encoding) can be performed in a router or inother network entities.

Wildcard Processing

[0130]FIG. 20 is a flow chart of a wildcard method 410. This methodillustrates an example of using a set of routing rules for a filter toconvert wildcards in expressions for subscriptions. Method 410 can beimplemented, for example, in software modules as represented by agent128 for execution by processor 134 in user machine 122. Alternatively,wildcards can be processed in the network by processor 93 under softwarecontrol in intelligent router 92 or in the corresponding functionscontained in ASIC 91. Wildcards include open fields or variable lengthfields, examples of which are provided in Table 21.

[0131] In method 410, agent 128 or other entity receives a subscriptionhaving a wildcard (step 412). The subject length for subscriptions canbe specified by a publisher when publishing content, and the subject canbe pre-processed on the publisher machine, for example, to count thefields of the subject and thus obtain a field count (length) for it.Agent 128 counts the number of fields in the filter operand (step 414)and initializes a new rule (filter) of field length=N (step 416). Agent128 retrieves a sub-field for the subscription (step 418) and determinesif the filter operand sub-field O[i] is a wildcard (step 420). If thefilter operand sub-field is not a wildcard, agent 128 adds a conjunctiveclause to the rule, field [i]=O[i] (step 422). If the filter operand hasmore sub-fields (step 424), agent 128 returns to step 418 to processadditional sub-fields. The parameter “i” represents a field where i isan integer representing the field number in this example.

[0132] After processing the sub-fields, agent 128 determines if the lastfilter operand sub-field is a “>” (step 426) and, if so, it changes thelength constraint to field length>N−1 (step 428). Wildcard processingcan use any type of symbol, and a “>” is only one such example. In thisexample, a “a.>” can mean a.b, a.c, a.d, etc. and all their sub-subjectsat all levels (for example, a.b.x, a.c.x, a.b.x.y, etc.). Other symbolscan be used for other implementations of wildcards.

[0133] If necessary, agent 128 propagates the transformed rule tointelligent routers or other entities in the network (step 430).Accordingly, the method iterates through the sub-fields in order toprocess them for conversion of the wildcards to non-wildcard rules,meaning rules that do not contain wildcards. The conversion of wildcardscan occur anywhere in the network, for example on the subscriber machineor in an intelligent router. The conversion can thus occur in one entitywith the transformed rule propagated to other entities or it can occurdynamically.

[0134] Table 23 provides a summary, along with examples, of theseexemplary routing rules for processing wildcards. These routing rulescan be generated in the intelligent routers, for example, or generatedin other network entities and propagated to the intelligent routers. Inaddition, the routing rules in Table 23 are provided for illustrativepurposes only and other routing rules are possible for convertingwildcards. TABLE 23 Original Rule Transformed Rule subject = “a.b”subject.length == 2 & subject[0] == “a” & subject[1] == “b” subject =“C.*.D” subject.length == 3 & subject[0] == “C” & subject[2] == “D”subject = “foo.>” subject.length > 1 & subject[0] == “foo” subject =“*.*.b.*.c.>” subject.length > 5 & subject[2] == “b” & subject[4] == “c”

Persistent and Reliable Massage Delivery

[0135] The embodiment described herein provides apparatus and methodsfor persistent storage of messages and recovery, restart and/orcontinuation of message flows in the face of network, link and/or nodefailures in a publish-subscribe network. Message persistence is theability to store messages and retrieve them at a later time. A largenumber of specific applications, e.g. email, generally require lengthymessage persistence for messages flowing through the network. In idealconditions, with no failures in the network an always-connectedsubscriber should not need any persistence beyond that required forthese specific applications. However, in reality, messages can get“lost” while traversing through the network due to various reasons—e.g.,(1) failures or buffer overflows occurring either inside the network orat the user end or (2) users doing an explicit disconnect from thenetwork and connecting back again after a time period.

[0136] The persistence model of an event notification platform of thepresent embodiment is divided into two levels: short-term persistenceand long-term persistence. Short-term persistence is designed forrecovering from packet loss due to network congestion or short-term linkfailure. Long-term persistence is designed for recovering from otherfailures including, e.g., loss of user connections, failure of usermachines, failure of applications, and/or longer-term network failure.

[0137] A channel (e.g., as described above) can either be persistent orreal-time. A real-time channel transmits data that is generally onlyuseful in real-time and does not have any application-specificpersistence requirements. A persistent channel stores data traversingthrough network for a persistence time frame T. In other words,persistence for a persistent channel is guaranteed for a time frame T.This persistence of data is achieved through the following, for example:caching data at each edge node for the persistent duration of a channel;retrieving data from the cache transparent to the users under failureconditions; allowing the user to explicitly retrieve data from thecache; making the flow of data through the network persistent byguarding against router failures and setting up reliable tunnels betweenrouters; and, protecting the channel components against failure throughreplication.

[0138] A. Persistence through Caching

[0139] Timed Persistence (with time frame T) is the ability to retrievethe last time frame T of data from the publish-subscribe network. Forexample, if a subscriber leaves the network, any data on a persistentchannel that is received during the subscriber's absence is held in thenetwork for a time frame T (from the data's receipt). If the userreturns within the time frame T, the user does not lose any data.

[0140]FIG. 21A is a block diagram illustrating certain components of apublish-subscribe subscribe network that provide persistence throughcaching. As shown, the network includes core routing nodes and an edgerouting node. Each routing node preferably includes an intelligentrouter 92 (shown with the edge routing node) and a conventional backbonerouter (not shown), as described above in FIG. 4. Each intelligentrouter 92 that needs to perform caching for persistent channelspreferably has a cache manager 218 co-located with it, as illustrated byFIG. 21A. The cache manager 218 is described above with references toFIG. 8. The intelligent router 92 is preferably responsible forshort-term persistence for retrieving lost data or recovering fromrouter failures. The cache manager 218 is responsible for caching datato provide long-term persistence for a channel. The cache manager 218preferably caches this data in the cache 540. The cache 540 preferablyincludes a memory and a disk (not shown). Also shown in FIG. 21A is anagent 128, which is preferably resident in subscriber machine 122 (notshown in FIG. 21A), as described above in FIG. 5. The agent 128 isresponsible for communicating with the cache manager 218 to retrievedata from the cache 540, receiving the retrieved data and for organizingthe retrieved data.

[0141] Although not shown in FIG. 21A, each of the first level of corerouting nodes upstream from the edge routing node preferably includes acache manager 218. Upstream is the direction moving away from the agent128 (i.e., away from the subscriber machine 122). The first level ofupstream core routing nodes refers to the routing nodes immediatelyupstream from the edge routing node. Although publish-subscribe networksoften include a plurality of first level upstream core routing nodes,FIG. 21A only depicts one first level upstream core routing node, corerouting node 548. As described above, a cache manager 218 provides forlocal caching of data at a network node at which it is located.Therefore, the operation of cache managers 218 located at various corerouting nodes, including, e.g., core routing node 548, provides fordistributed caching of data throughout the network core. Thisdistributed caching provides a backup for the caching at edge routingnode.

[0142] Cache manager 218 preferably includes routines or sub-routinesresponsible for managing the cache 546. These routines preferablyinclude a caching data routine 545, purging cache data routine 547 andretrieving cache data routine 549, as illustrated in FIG. 21B. Each ofthese routines may operate separately or, as shown, may communicateand/or pass control between one another.

[0143]FIG. 21C is a flow chart illustrating an example method ofpersistent caching 550 for data contained in a single message. As shown,the method 550 shows an exemplary execution of steps performed by eachroutine shown in FIG. 21B. In operation, these routines preferablyoperate independent of one another. Method 550 may be performed at anintelligent router 92, at an edge routing node or core routing nodes,that provides caching.

[0144] The method 550 can be implemented, for example, in softwaremodules (e.g., cache manager 218) for execution by a processor 93 inintelligent router 92. Alternatively, it can be implemented in an ASICor a combination of hardware and software, either in the same ordifferent physical device as a corresponding intelligent router 92. Theintelligent router 92 forwards messages that need to be cached to thecache manager 218. The cache manager 218 receives the messagescontaining data (step 552), time marks the data in the messages (step554), and caches the data in the cache 546 (step 556) (analogous tosteps 322-326 in FIG. 14 (see above)). The cache manager 218 indexes thecached data (step 558) in a number of ways, e.g., channel identifier,subjects, publisher identifier, timestamp etc, as described above. Theindexing step 558 may take place prior to, simultaneously with, or afterthe caching step 556. The cached data may be indexed and stored in ahierarchical directory structure (e.g., see FIG. 15). See also Tables17-19.

[0145] The data is cached in memory (the cache 546) and periodicallymoved to disk (step 560). A persistent time frame “T” for a particularchannel is divided into N time grains each of size G. The caching inmemory (step 556) is only for the duration of G. After the cache managerdetermines that time interval G has passed (step 559), the data is movedto the disk (step 560). The cache manager 218 stores the data on thedisk for the duration of persistent timeout interval T.

[0146] The data corresponding to a time interval G is deleted from thedisk (step 564) once the time becomes greater than the Persistenttimeout (T) for the channel+the upper limit of the interval (step 562).To better understand this, suppose a channel has a T of 2 hours. As anexample, the cache manager 218 uses a time granularity G of 15 minutes.For deleting the data from the disk, the policy preferably used is thatwhen the last data cached during a time interval G (15 minutes) has beenstored for T (2 hours), the entire data cached during that 15-minuteinterval will be discarded. Therefore, the data cached in the beginningof that 15-minute interval will have been stored for longer than 2 hoursbefore it is deleted. In this example, the data cached during each15-minute interval is a block of data. If the persistent time frame T isdivided into N intervals, any point in time there will be N+1 blocks ofdata (N on disk and 1 in memory) in the cache 540 for each subject.

[0147] If the cache manager 218 receives a request for data (step 566),the cache manager 218 retrieves that requested cached data (for whichtime T has not passed), using the index (step 568) and transfers theretrieved data to the backbone router for routing to the requestingsubscriber machine 122 (step 570). As described below, with reference toFIG. 21D, if the data is not at the cache 540 at the edge routing node,the cache manager 218 may invoke caches at the first level of upstreamcore routing nodes (e.g., at core routing node 548) to retrieve thedata. If the cache manager 218 does not receive a request, method 550loops back to step 552.

[0148] To guard against failures of the cache manager 218 at a givenintelligent router 92, in addition to storing data in the cache 546, thedata is also stored in caches at the first level of upstream corerouting nodes (e.g., core routing node 548). Hence, steps 552-564 arepreferably performed at the first level of upstream core routing nodesprior to the messages being routed to and method 550 being performed atthe edge routing node.

[0149] The locations of the cache 546 (e.g., at the edge routing node)and the caches at the first level of upstream core routing nodes (e.g.,at the first upstream core router 548) are stored locally in the agent128. Therefore, if the subscriber machine 122 moves (e.g., thesubscriber is a mobile subscriber that re-connects to the network at adifferent edge routing node), the agent 128 will provide the new edgerouting node with the location of the caches for the edge routing nodeand first level of upstream core routing nodes to which the subscribermachine 122 was connected prior to moving. This enables persistence tobe maintained even if the subscriber machine 122 moves.

[0150] As seen in FIG. 21D, a flowchart of a method of persistentmessage retrieval 580, a user application 182 at subscriber machine 122preferably invokes the agent 128 to request data from the cache (step582). Using the stored cache locations, the agent 128 invokes the cache546 at the appropriate edge routing node (e.g., using a getcachecommand) to get the data (step 584). The agent 128 may indicate whattime frame of data to retrieve. Alternatively, the cache manager 218 maycheck the connection history of a subscriber machine 122 (see Table 18above) to determine what cached data to retrieve. If the connectionhistory indicates that the subscriber machine 122 was off-line for Xperiod of time, the cache manager 218 may retrieve all available cacheddata for X. Additionally, the cache manager 218 may simply retrieve alldata cached within persistent time frame T. If the edge routing nodecache 546 has the data (step 585), the agent 128 retrieves the data fromthe cache 546 (step 586).

[0151] If the cache 546 does not have the data, the cache manager 218uses a list of the caches at the first level of upstream routing nodes(e.g., core routing node 548) provided by the agent 128 to invoke theseupstream caches to locate the data (step 588). Once the cache manager218 locates the data in an upstream cache or caches, the cache manager218 retrieves the data from the upstream cache(s) (step 590). The cachemanager 218 may perform duplicate suppression (i.e., eliminate duplicatedata) (step 592) before forwarding the data to the agent 128 (step 594).

[0152] B. Persistence through Failure Protection

[0153] An infrastructure consistent with the present embodiment has thefollowing components or equivalent components: channel managers; eventagent; and, routing nodes and caches. To guard against loss of messagesduring failure conditions, each of these components needs to beprotected.

[0154] 1. Channel Manager Fault Protection

[0155] Channel managers are described above with reference to FIG. 6.The channel managers are protected from failures through replication.The channel managers operate in a primary-backup group, where there isone primary module and the other backup modules. The primary module isresponsible for all updates to the data and also responds to queries.The backup can only serve queries but cannot perform updates. Itforwards all updates to the primary.

[0156] Components of the publish-subscribe network that need to retrievechannel information from the channel managers are referred to as channelmanager clients and are assigned a channel manager. These clientsinclude intelligent routers 92, and their cache managers 218, andsubscriber machines 122, and their agents 128. If the channel managerassigned to the client fails, the client accesses another channelmanager and connects to it.

[0157] 2. Routers and Cache Fault Protection

[0158] There are several levels of recovery for the routinginfrastructure components. (Level 0, Level 1, through Level 3). Level 0controls the failure effect locally (i.e., within the failed router) andthe recovery is also limited to the failed routing node. Level 0recovery depends on hardware redundancy to recover from hardwarefailures. The hardware resources in a router are replicated. The mainadvantage of level 0 recovery is the short recovery time andtransparency. Level 1 controls the failure effect within a LAN. Level 1recovery may be implemented with IP fail-over using cluster technology.However, tunnels of a failed router to its neighbors have to bereconstructed after recovery. Therefore, level 1 recovery is lesstransparent and takes longer than level 0 recovery.

[0159] The scope of Level 2 recovery is to recover router failure byremote backup router over a WAN, without affecting network topology,which may cause complex reconfiguration and data loss. Level 2 may beimplementing by grouping routers to form a recovery set (e.g., a primaryand backup router). One router may be a primary in one group and abackup for another group. The primary exchanges routing and networkconfigurations with the backup, and when the backup detects a failure ofthe primary, it takes over the functions of the primary. The backupensures that the primary router failed, and not the link to the primaryrouter, by ensuring that it can connect to the majority of neighborprimary routers of the failed primary router. If it cannot, level 3recovery is triggered.

[0160] Level 3 on the other hand may involve a system-wide coordinatedrecovery. Level 3 is used when all else fails. The router that detectssuch a failure sends a restart notice to all downstream routers. Therouters receiving the notice, suspend all other recovery, stop allnetwork services, and discard all multicasting information in therestart message. After all network services have been terminated, therouter restarts all services, including tree-building process formulticasting. Any failure in the network is treated by a lower levelrecovery procedure. If a lower level recovery cannot be applied, therecovery is escalated to the next higher level. If none of the lowerlevel recoveries work, the level 3 recovery is used.

[0161]3. Reliable Tunnels

[0162] To guard against loss of messages during network failures, areliable tunnel is used to carry traffic between routing nodes. Tunnelsare described above in the description of FIG. 3. Any message lossesduring transmission are detected by the receiving end, which then asksthe sender to retransmit the lost messages.

[0163] While the present invention has been described in connection withan exemplary embodiment, it will be understood that many modificationswill be readily apparent to those skilled in the art, and thisapplication is intended to cover any adaptations or variations thereof.For example, various types of publisher machines, user or subscribermachines, channels and configurations of them, and hardware and softwareimplementations of the content-based routing and other functions may beused without departing from the scope of the invention. This inventionshould be limited only by the claims and equivalents thereof.

1. A method for providing persistent caching of messages delivered via apublish-subscribe network, comprising the steps of: (a) receiving, at afirst node, a message having data via the network; (b) time-marking thedata; (c) caching the data in a cache memory at the first node; and (d)routing the message to a second node using content-based routing.
 2. Themethod of claim 1, further comprising the step of: (e) repeating steps(a) through (d) at the second node, wherein the data is cached in acache memory at the second node.
 3. The method of claim 1, furthercomprising the steps of: determining if a time granularity G has passedsince the caching step (c); and moving the cached data from the cachememory to a disk based on a determination that G has passed.
 4. Themethod of claim 1, further comprising the steps of: determining if apersistent time-frame T has passed since the caching step (c) for a lastblock of the cached data; and deleting the cached data based on adetermination that T has passed for the last block of the cached data.5. The method of claim 4, wherein T is set based on a channel with whichthe data is associated.
 6. The method of claim 1, wherein the first nodecomprises an intelligent router and the receiving step (a) receives themessage at the intelligent router.
 7. The method of claim 6, wherein theintelligent router includes a cache manager and the cache managerperforms steps (b) and (c).
 8. The method of claim 1, wherein the secondnode comprises a subscriber machine.
 9. A router for providingpersistent caching of messages delivered via a publish-subscribenetwork, comprising modules for executing the method of claim
 1. 10. Apublish-subscribe network for providing persistent caching of messages,comprising nodes that include modules for executing the method of claim2.
 11. A computer-readable medium comprising instructions for executingthe method of claim
 1. 12. A method for providing persistent caching ofmessages delivered via a publish-subscribe network, comprising the stepsof: receiving a message having data via the publish-subscribe network;time-marking the data; caching the data in a cache memory; determiningif a time granularity G has passed since the caching step; moving thecached data to a disk based on a determination that G has passed;determining if a persistent time-frame T has passed since the cachingstep for a last block of the cached data; and deleting the cached datafrom the disk based on a determination that T has passed for the lastblock of the cached data.
 13. The method of claim 12, further comprisingthe step of determining whether a request for the cached data has beenreceived.
 14. The method of claim 13, wherein the request for the cacheddata is received from a user machine.
 15. The method of claim 13,further comprising retrieving the cached data based on a determinationthat a request for the cached data has been received.
 16. The method ofclaim 15, wherein the retrieving step comprises invoking an upstreamcache and retrieving the cached data from the upstream cache.
 17. Themethod of claim 16, further comprising performing duplicate suppressionon the cached data retrieved from the upstream cache.
 18. The method ofclaim 16, wherein the retrieving step obtains a listing of upstreamcaches from a user machine agent.
 19. The method of claim 15, furthercomprising the step of transferring the cached data to a backbone routerfor routing to a user machine.
 20. The method of claim 12, furthercomprising the step of indexing the cached data.
 21. The method of claim20, wherein the indexing step indexes the cached data by channel ID,subjects and/or time stamps.
 22. The method of claim 12, furthercomprising the steps of performing the receiving, time-marking andcaching steps at an upstream routing node.
 23. The method of claim 12,further comprising the step of repeating the receiving step.
 24. Arouter for providing persistent caching of messages delivered via apublish-subscribe network, comprising modules for executing the methodof claim
 12. 25. A publish-subscribe network for providing persistentcaching of messages, comprising a first node and a second node, whereinthe first node is upstream from the second node and the first node andthe second node each include modules for executing the method of claim12.
 26. A computer-readable medium comprising instructions for executingthe method of claim
 12. 27. A method for providing persistent caching ofmessages delivered via a publish-subscribe subscribe network, comprisingthe steps of: (a) receiving a plurality of messages having data via thenetwork at a plurality of upstream nodes; (b) time-marking the data; (c)caching the data in cache memories at one or more of the plurality ofupstream nodes; (d) routing the messages to an edge node usingcontent-based routing; and, (e) repeating steps (a) through (c) at theedge node, wherein the data is cached in a cache memory at the secondnode.
 28. The method of claim 27, further comprising the step of routingat least one of the messages from the edge node to a subscriber machineusing content-based routing.
 29. The method of claim 28, furthercomprising the step of the edge node receiving a request for cached datafrom the subscriber machine.
 30. The method of claim 29, furthercomprising the steps of: determining a time-amount of cached data toretrieve in response to the request; and, retrieving the determinedtime-amount of cached data based on the time-mark of the cached data.31. The method of claim 30, wherein the time-amount is determined fromthe request, wherein the request includes a requested time-amount ofcached data to be retrieved.
 32. The method of claim 30, wherein thetime-amount is determined by calculating a disconnected time for thesubscriber machine, wherein the disconnected time is the amount of timethat the subscriber machine was disconnected from the publish-subscribenetwork.
 33. The method of claim 29, further comprising the step ofdetermining that at least some requested cached data is stored at one ormore of the plurality of upstream nodes.
 34. The method of claim 33,further comprising the step of the edge node receiving a list ofupstream nodes from the subscriber machine.
 35. The method of claim 33,further comprising the steps of: communicating the request for cacheddata to one or more of the plurality of upstream nodes; retrievingrequested cached data from the one or more of the plurality of upstreamnodes; and, routing the retrieved data to the subscriber machine. 36.The method of claim 35, further comprising the step of performingduplicate suppression on the retrieved data.
 37. A publish-subscribenetwork for providing persistent caching of messages, comprising aplurality of upstream nodes and an edge node, wherein the nodes includemodules for executing the method of claim 27.